Canon

The canons used to be those persons who resided in the
buildings contiguous to the cathedral, employed either in the daily
service, or in the education of the choristers. The word is Greek, and
means a measuring rod, the beam of a balance; then, a roll or register
containing the names of the clergy who are licensed to officiate in a
cathedral church.

Canon.

A divine or ecclesiastical law.

Or that the Everlasting had not flxed
His canon 'gainst self-slaughter.